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Field  Columbian   Museum 

Publication  35. 

Geological  Series.  Vol.  I,  No.  5. 


A    FOSSIL    EGG    FROM 
SOUTH    DAKOTA 


BY 


Oliver  Cummings  Farrington,  Ph.D., 
Curator,  Department  of  Geology. 


Chicago,  U.  S.  A. 

/ 


April,  1899.      £ 


A  FOSSIL  EGG  FROM  SOUTH  DAKOTA. 


The  specimen  (Museum  No.  P  5734)  described  in  this  paper  is 
believed  by  the  author  to  be  a  petrified  egg  of  an  Anatine  bird  of 
Early  Miocene  age.  If  this  supposition  be  correct,  the  specimen 
seems  to  warrant  description  both  as  an  interesting  case  of  petrifac- 
tion and  as  indicating  the  presence  of  aquatic  birds  about  the  waters 
of  the  great  lake  which  is  generally  considered  to  have  occupied 
in  early  Tertiary  times  the  region  where  the  specimen  was  found. 
The  original  finder  of  the  specimen  was  Mr.  Kelly  Robinson  of 
Dakota  City,  South  Dakota.  He  stated  to  the  writer  that  while 
riding  one  day  in  the  summer  of  1896  in  the  region  of  the  Bad 
Lands  he  saw  this  object  lying  at  the  foot  of  "a  bad  land"*  and 
in  a  shallow  gully.  It  had  apparently  washed  there  from  "the  bad 
land  "  above.  Mr.  Robinson  picked  it  up  and  concluding,  on  exami- 
nation, that  it  was  a  petrified  egg,  took  it  home  for  a  curiosity. 
From  him  it  was  obtained  by  the  writer  for  the  Museum  in  the 
winter  of  1897.  The  specimen  is  not  quite  completely  ovoid  in  form 
since  from  one  end  a  portion  has  been  broken  away.  Mr.  Robinson 
stated  that  this  portion  was  missing  when  he  found  the  specimen. 
The  form  of  the  specimen  is  fully  indicated  by  Figs.  1,  2  and  3,  PI. 
XX,  where  are  shown  photographs  of  it  in  three  different  positions. 
As  may  be  seen  from  these  figures,  the  resemblance  of  the  specimen 
both  in  form  and  structure  to  an  egg  is  very  striking.  Covering  most 
of  the  exterior  is  a  thin,  black  layer  .017  of  an  inch  in  thickness 
which  closely  resembles  in  thickness  and  appearance  an  egg  shell. 
Within  this  and  constituting  the  major  portion  of  the  specimen,  is  a 
mass  of  pale  gray  translucent  chalcedony,  corresponding  in  appear- 
ance and  amount  to  the  white  of  air  egg.  Near  one  side  but  enveloped 
in  the  preceding  is  a  white,  opaque,  ovoid  mass  .66 of  an  inch  in  diam- 
eter which  can  be  easily  seen  to  correspond  in  size  and  position  to 
the  yolk.  If  the  specimen  be  not  a  petrified  egg,  therefore,  it  is  as 
perfect  an  imitation  of  one  in  external  appearance  as  can  be  con- 
ceived of. 

In  order  to  determine  the  existence  of  any  special  characters  in 
the  mineral  matter  of  the    specimen  this  was  studied    somewhat  in 

*  In  modern  Western  parlance  M  a  bad  land  "  is  any  knoll  or  slope  barren  of  vegetation. 

193 


194  Field  Columbian  Museum — Geology,  Vol.  i. 

detail.  The  portion  which  may  sufficiently  be  designated  as  the  shell, 
was  found  to  be  translucent  chalcedony  similar  to  that  of  the  main 
mass,  or  what  may  be  called  the  white,  and  for  the  most  part  con- 
fluent with  it.  It  is,  however,  dark  brown  to  black  in  color.  On 
heating  to  redness  this  color  disappeared,  indicating  organic  matter 
to  be  the  coloring  ingredient.  In  one  or  two  spots  the  shell  was  not 
homogeneous  throughout,  a  thin  white  layer  separating  it  from  the 
main  portion.  This,  on  testing,  proved  to  be  carbonate  of  lime,  indi- 
cating that  here  some  of  the  original  shell  had  not  been  replaced  by  the 
petrifying  siliceous  solutions.  No  definite  structure  or  markings  could 
be  distinguished  on  the  shell.  While  generally  smooth  in  outline,  under 
a  lens  it  is  seen  to  be  rough  and  porous,  owing  doubtless  to  the  action 
of  the  infiltrating  waters.  The  original  markings,  if  any,  must  have 
been  destroyed  by  such  an  action. 

The  portion  designated  as  representing  the  white  of  the  egg  is, 
as  has  been  said,  made  up  of  pale  gray  translucent  chalcedony.  It  is 
homogeneous  throughout  except  for  occasional  black  blotches,  some 
of  which  resemble  in  arrangement  those  of  moss  agate,  while  others 
show  concentric  distribution.  It  could  not  be  determined  without 
sacrificing  too  much  of  the  specimen,  whether  these  were  formed  by 
organic  matter  or  by  mineral  matter  such  as  oxides  of  iron  or  man- 
ganese. The  chalcedony  resembles  in  its  characters  that  of  the 
veins  of  that  mineral  which  traverse  the  region  and  which  have  been 
described  by  other  authors.*  On  heating  fragments  of  the  chal- 
cedony it  turns  white  and  opaque  but  yields  only  a  trace  of  water.  It 
is  infusible  and  has  a  hardness  of  7. 

It  is  to  the  portion  designated  as  the  yolk  that  the  greatest  inter- 
est attaches.  This  has  already  been  described  as  a  white  opaque 
ovoid  mass  .66  inch  in  diameter,  enveloped  in  the  chalcedony.  On 
close  examination  this  white  mass  can  be  seen  to  be  made  up  of  two 
portions  of  about  equal  size  which  have  different  structure.  That 
nearer  the  center  of  the  egg  is  made  up  of  little  spherules  and  thin 
curving  plates.  The  spherules  average  about  1  mm.  in  diameter  and 
have  a  distinct  concentric  structure,  coats  of  alternately  opaque  white 
and  translucent  dark  matter  being  deposited  around  each  center.  So 
far  as  can  be  judged  from  the  color  of  these  coats  they  are  opal  and 
chalcedony,  respectively,  but  color  is  not,  of  course,  in  such  a  case, 
an  accurate  criterion.  The  thin  curving  plates  are  similarly  made  up 
of  white  and  dark  layers. 

The  other  portion   of   the  "yolk"  is  composed  of  a  yellowish- 

*J.  B.  Hatcher,  Am.  Naturalist,  March,  1893,  p.  218.  E.  C.  Case,  Am.  Geologist,  April,  18^5, 
p.  248. 


Apr.  1899.    A  Fossil  Egg  from  South  Dakota — Farrington.      195 

white  opalescent  substance  quite  homogeneous  except  for  occasional 
darker  spherules,  which  show  a  concentric  structure  similar  to  those 
of  the  other  portion.  The  opalescent  substance  appears  both  in  its 
chemical  and  optical  characters  to  be  true  opal.  It  is  considerably 
cracked.  It  is  infusible  B.  B.,  but  has  a  hardness  less  than  7.  On 
heating  in  the  closed  tube  it  gives  off  'a  little  water,  turns  black  in 
spots  and  emits  a  distinct  odor  of  burning  nitrogeneous  matter. 
This  I  conjecture  to  come  from  some  of  the  original  organic 
matter  of  the  egg,  which  has  not  as  yet  been  replaced  by  siliceous 
matter.  As  such  an  occurrence  had  not  come  within  my  observation 
before,  I  thought  it  well  to  test  some  other  petrified  substance  to  learn 
if  it  contained  any  organic  residue.  Accordingly,  fragments  of  the 
well-known  petrified  wood  from  Sonoma  County,  California,  were  put 
to  a  similar  test,  and  somewhat  to  my  surprise  an  odor  of  smoking 
wood  was  distinctly  given  off.  It  therefore  seems  probable  that  in 
many  petrified  substances  some  of  the  original  organic  matter  may 
remain  imprisoned. 

In  order  to  determine  whether  any  remains  of  cell  structure  were 
to  be  observed,  a  fragment  from  the  portion  where  the  " white"  and 
"yolk  " — in  other  words,  the  chalcedony  and  opal — join,  and  which 
showed  as  well  a  spherule  of  chalcedony,  was  ground  thin  for  micro- 
scopic examination.  As  shown  by  the  drawings,  Figs.  1  and  2,  noth- 
ing like  cell  structure  is  to  be  seen  in  the  section.  The  chalcedonic 
portion  shows  several  spherules,  but  these  do  not  differ  in  character 
from  those  usual  to  chalcedony.  In  the  portion  made  up  of  opal  an 
elongated  cavity  is  to  be  seen  which  suggests  in  form  a  compressed 
air  bubble.  This  is  lined  with  two  successive  layers  which  may  fol- 
low some  membranous  structure,  but  of  this  there  is  no  certainty. 
The  portion  of  the  section  made  up  of  opal,  when  viewed  in  ordinary 
light,  is  of  a  yellowish-brown  color,  and  shows  no  other  structure 
than  that  mentioned.  In  polarized  light  it  becomes  wholly  dark, 
showing  its  amorphous  and  singly  refracting  character.  The  portion 
made  up  of  chalcedony  is  colorless  in  ordinary  light  except  for  the 
spherules  previously  mentioned.  These  are  bounded  by  a  thin,  yel- 
low ring,  within  which  is  a  transparent  area,  and  within  this,  making 
up  the  central  portion,  is  another  yellow  mass,  having  a  distinctly 
radiated  fibrous  structure.  The  general  appearance  of  the  spherules 
in  ordinary  light  is  thus  very  much  like  that  of  those  of  the  siliceous 
oblite  of  Pennsylvania,  which  has  been  described  by  Barbour  and 
Torrey*  and  E.  O.  Hovey.f 

•  Am.  Jour.  Sci..  3d  Ser.,  Vol.  XL,  p,  246. 
t  Bull.  Geol.  Soc.  of  America.  Vol.  V,  p  627. 


196 


Field  Columbian  Museum — Geology,  Vol.  i. 


In  polarized  light  the  yellow  outer  ring  of  the  spherules  remains 
dark  during  a  revolution,  indicating  it  to  be  opal.  The  interior  portion 
assumes  an  appearance  like  that  of  granularquartz.  This  is  similar  to 
that  described  by  Hovey  as  characterizing  the  interior  of  some  of  the 
spherules  of  the  Pennsylvania  oolite.  The  spherulitic  interference 
cross  is,  however,  clearly  to  be  seen,  and  the  optical  character  is  nega- 
tive. Hence  the  method  of  formation  can  not  be  regarded  as  similar 
to  that  proposed  by  Hovey  for  the  siliceous  oolite,  but  is  probably  a 
simple  spherulitic  structure,  in  accordance  with  which  any  foreign 
matter,  such  as  the  opal,  was  arranged.  The  main  portion  of  the 
chalcedony  shows  a  typical  radially  fibrous  structure 


I  DRAWN    WITH    CAMKRA    LUCIDA. 


Fig.  1.  Section  from  "  yolk  "  in  ordinary 
, 'light-  Dark  portion  opal;  light  portion,  in- 
cluding spherules,  chalcedony. 

X22. 


FlG.  2.  Same  in  polarized  light.  The 
opal  becomes  black;  the  chalcedony  shows  a 
fibrous  structure  and  the  spherules  interfer- 
ence crosses. 

X22. 


A  section  of  chalcedony  from  the  veins  of  the  region,  studied  for 
comparison,  showed  a  similar  strongly  marked  fibrous  character  and 
tendency  to  radial  arrangement. 

The  specific  gravity  of  the  specimen  as  a  whole  was  found  to  be 
2.594,  or  about  that  of  chalcedony. 

It  is  of  course  desirable,  if  possible,  to  obtain  an  explanation  of 
the  way  in  which  so  unique  a  case  of  petrifaction  could  occur,  if 
petrifaction  it  be.  I  have  been  unable  to  find  any  account  of  a  simi- 
lar occurrence  as  having  been  noted  before.  The  fossil  Chelonian 
eggs  of  Tertiary  age  from  Auvergne,  France,  are  simply  shells  filled 
with  hardened  mud.     The  fossil  eggs  of   the  New  Zealand  birds  are 


Apr.  1899.    A  Fossil  Egg  from  South  Dakota — Farrington.      197 

likewise  only  shelis,  which  have  been  preserved  by  reason  of  their 
thickness.  Neither  of  these  occurrences  are,  therefore,  cases  of  true 
petrifaction.  At  first  thought,  an  egg  of  the  sort  here  described 
may  seem  too  perishable  for  preservation  by  a  process  of  true  petri- 
faction. It  is  difficult  to  understand  how,  in  such  a  mass  as  an  egg, 
petrifying  liquids  could  pass  to  and  fro,  removing  particles  of  organic 
matter  and  replacing  them  by  particles  of  silica,  in  the  way  that  it  is 
generally  understood  that  petrifactions  usually  take  place.  On  further 
consideration,  however,  the  natural  petrifaction  of  an  egg  need  not 
seem  to  be  an  impossible  phenomenon.  If  covered  as  soon  as  de- 
posited, by  mud  or  earth,  as  it  is  likely  to  have  been  in  this  region, 
its  substance  might  endure  for  months  or  years.  Or,  the  process  of 
petrifaction  might  have  begun  at  once,  since  the  present  chalcedony 
veins  of  the  region  show  that  circulating  siliceous  waters  are  abund- 
ant there. 

Given  conditions  of  this  sort,  I  believe  that  petrifaction  could  have 
gone   on   by  a   process  of   endosmose  and  exosmose  similar  to  that 
believed  by  M.  Forster  Heddle*  to  produce  the  formation  of   agates. 
As  the  cases  seem  so  similar  in   their  conditions,  his  theory  may  be 
quoted  in   full:      ''We  have  now  a  cavity  slightly  lined  with  chalce- 
donic  matter,  containing,  within,  water  more  or  less  pure,  while  with- 
out (that  is,  outside  the  now  double  skin,  delessite  and  first  layer), 
we   have  a  strong  solution  of    colloidal    silica    constantly   supplied. 
Endosmose  and  exosmose  are  set  up  with  resistless  force.      The  strong 
solution   finds  its  way  through  the  two  or  any  number  of  increasing 
skins;  the  weak  water  is  forced  out  through  the  point  of  infiltration, 
and   so  in   its  passage  out  thins  all  the  successively  deposited  layers 
at  that  place.      By  the  continuous   flow  of   colloidal  silica  (held   in 
solution  by  liquid)  through  the  already  coagulated  or  deposited  layers, 
continuous  coagulation  of  the  silica  in  the  yet  hollow  agate,  and  con- 
tinuous extrusion  of  the  residual  water,  we   have  the  ultimate  filling 
up  of  the  cavity,  and  a  solid  agate  formed."     The  parallelism  of  con- 
ditions in  the  two  cases  is  so  apparent  as  to  need  no  emphasis.      The 
shell   of  the  egg  and   its   lining   membrane   furnish  the  "skin,"  the 
albuminous  or  watery  substance  within  the  egg  the  weak  solution,  and 
the  circulating  siliceous  waters  known  to   abound  in   the   region  the 
strong  solution  of  colloidal  silica.      Or  the  positions  of  the  latter  may 
have   been  reversed,  the  thicker  liquid   having   been  within  and  the 
thinner  without.      In   either   case    a   transference  would   take   place. 
While  I  cannot  say  that  Professor  Heddle's  theory,  that  agates  have 
been  formed  in  this  way,  is  altogether  the  adopted  one,  the  stages  of 

*  Nature,  Vol.  XXIX,  p.  419. 


ig8  Field  Columbian   Museum — Geology,  Vol.  i. 

the  process  as  he  describes  them  at  least  seem  logical  and  reasonable, 
and  may  well  have  brought  about  petrifaction  in  the  case  of  an  egg.  Of 
course  it  is  not  held  as  proved  that,  in  the  specimen  under  considera- 
tion, those  portions  which  I  have  designated  as  white  and  yolk  have 
been  preserved  in  their  original  structure  and  proportions.  While  this 
may  be  the  case,  it  is  again  quite  as  likely  that  the  portion  which  I 
have  designated  as  the  yolk  represents  the  shrunken  residue  of  the 
egg  substance  as  a  whole.  Its  appearance,  indeed,  rather  indicates 
this,  since  the  curved  plates  that  have  been  described  resemble 
shrunken  membranes.  The  remainder  of  the  interior  may  then  have 
been  filled  simply  with  water  at  the  time  petrifaction  set  in. 

It  is  more  difficult  to  explain  the  fact  that  most  of  the  "  yolk  "  is 
composed  of  opal  while  the  rest  of  the  interior  is  made  up  of  chalce- 
dony. The  difference  is,  however,  not  essentially  greater  than  that 
often  found  to  exist  in  different  layers  of  agates. 

For  establishing  any  conclusions  as  to  the  nature  of  the  parent 
of  the  egg,  no  other  data  are  available  than  its  form.  For  a  knowl- 
edge of  what  this  indicated  I  referred  to  Mr.  Wm.  A.  Bryan  of  the 
Museum,  who  has  very  kindly  furnished  the  following  report:  "The 
form  of  the  specimen  suggested  to  me  on  the  first  examination  that 
it  was  that  of  an  egg  of  one  of  the  Anatidae  or  Duck  family.  Further 
study  confirmed  this  conclusion,  the  similarity  in  form  to  that  of  eggs 
of  Anatine  birds  being  marked  and  such  as  to  distinguish  it  from  the 
eggs  of  birds  of  other  families.  Measurements  of  the  fossil  egg,  too, 
showed  it  to  have  the  same  proportions  as  those  of  members  of  the 
Anatida1,  while  they  differed  to  a  marked  degree  from  those  of  other 
families.  These  similarities  and  differences  are  illustrated  in  the 
eggs  shown  in  PI.  XXI.  The  eggs  there  shown  were  selected  to 
represent  as  nearly  as  possible  types  having  the  general  oological 
characters  of  the  different  families  of  birds  whose  eggs  might  resem- 
ble the  fossil  form,  or  whose  habits  would  lead  them  to  deposit  eggs 
under  conditions  favorable  for  petrifaction.  To  complete  the  form 
of  the  fossil  egg  for  this  purpose,  the  outline  on  the  broken  end  was 
filled  out  with  plaster.  By  this  method  the  form  of  the  egg  was 
reproduced,  any  error  being  probably  within  T^  of  an  inch.  The 
measurement  of  length   was   therefore  made  on  this  completed  egg." 


Apr.  1899.    A  Fossil  Egg  from  South  Dakota — Farrington.     199 

"The  following  table  shows  the  species  of  eggs  chosen  and  their 
measurements:  " 


No. 


Order. 


Family. 


Species. 


Common  Name. 


Measurements, 
(ling,  inches.) 


Anseres 

Longipennis. 

Gallinae 

Limicolae. . . 


Anatidic. 
Laridae.  . 


Tetraonidae. . 
Charadiida?. . 


Anas  fulvigula 
(Sterna     fuligi- 

)     nosa 

(Tympanuchus 
}  americanus. 
(Charadriusdo 
I     minicus 


Prairie  Hen 


Herodiones. .  .'■  Ardeida?. 


Pygopodes.. . . 
Steganopodes. 


Podicipida 

(Phalacrocora- 
/     cidae 


Ardea  caerulea 

(Pod  i  lymbus 

)     podiceps 

Phalacrocorax 
p.  robustus. . . 


Fossil  Egg.. . . 
Florida  Duck 

f Sooty  Tern.. . . 

s 

American/ 
Golden  Plover^ 
\Little  niue^ 

/     Heron ) 

Pied  -  billed  \ 

Grebe ) 

Violet  Green/ 
Cormorant.^ 


2.03  X  1  49 
2.05  X  1.52 

1.84  X  1.28 

1.72  X  i.?8 
1.86  X  1.40 

1 . 73  X  1 .  30 
1. 71  X  1. 19 
2.52  X  1. 5 1 


It  will  be  seen  that  in  form  and  proportional  measurements  the 
fossil  egg  resembles  most  closely  that  taken  as  the  type  of  the  Anat- 
idae.  The  probability  of  its  parent  belonging  to  that  family  is  also 
increased  when  one  considers  the  nature  of  the  formation  in  which 
the  egg  was  found.  This  is  of  lacustrine  origin,  and  birds  of  this 
family  are  well  known  to  frequent  the  waters  of  lakes.  Unfortunately, 
from  the  manner  in  which  the  egg  was  found,  it  cannot  be  stated 
positively  that  it  came  from  the  beds  immediately  adjacent.  These 
are  of  White  River  age,  but  as  the  specimen  was  not  found  in 
situ  it  may  of  course  have  come  from  later  and  higher  beds,  or, 
as  has  been  suggested,  be  even  an  egg  of  a  comparatively  modern 
bird.  Yet  the  probabilities  are  strongly  in  favor  of  the  supposition 
that  the  specimen  was,  until  just  before  it  was  found,  imbedded  in 
the  formation  immediately  adjacent,  and  was  brought  to  light  by 
erosion,  just  as  bones  of  extinct  vertebrates  are  continually  being 
exposed  in  the  same  region  at  the  present  time.  If  these  suppositions 
are  correct,  the  specimen  affords  evidence  of  the  existence  of  birds  of 
the  order  Anatidae  in  Early  Miocene  times. 

The  only  other  mention  of  the  finding  of  bird  remains  in  rocks  of 
this  period,  in  this  country,  of  which  I  am  aware,  is  that  of  two 
species  of  birds  from  the  Amyzon  shales  of  Nevada.  These  re- 
mains consist   of  scattered   bones   and  feathers,  and  represent  birds 


200  Field  Columbian  Museum — Ge'ology,  Vol.  i. 

one  species  of  which  has  been  described  by  J.  A.  Allen*  as  a  passerine 
bird  of  the  family  Fringillidae,  the  other  by  E.  D.  Copef  as  a  species 
of  the  order  Grallae  and  tribe  Limicolae. 

In  conclusion,  the  hope  may  be  expressed  that  if  any  specimens 
of  similar  character  are  known  they  will  be  fully  described,  so  that 
more  evidence  may  be  at  hand  to  clear  up  the  difficulties  encountered 
in  the  study  of  this  one.  I  have  reports  of  the  finding  of  at  least  two 
other  petrified  eggs  at  different  times  in  the  same  region,  but  have 
been  quite  unable  to  verify  the  reports  or  see  the  specimens.  A 
systematic  study  of  the  forms  of  eggs  seems  also  desirable,  so  that  in 
the  future  definite  conclusions  may  be  drawn  regarding  the  order 
or  family  to  which  a  parent  belonged  when  an  egg  is  the  only  relic  of 
the  parent  to  be  obtained. 

•Bull.  U.  S.  Geol.  Surv.  Terrs.,  IV,  1878.  p.  443.  PL  I. 

tRept.  U.  S.  Geol.  Surv.  Terrs.,  Vol.  Ill,  Book  I,  p.  754.  PL  LIX. 


FIELD   COLUMBIAN    MUSEUM. 


GEOLOGY,    PL.  XXI. 


Fossil  Egg  and  Eggs  Resembling  It  in  Form  and  Probable  Habitat  of  Parent. 


La* 


